This study represents one portion of a major program in our laboratory whose objectives are to 1) understand the mechanisms of action involved in the selective radio- and chemosensitization of neoplastic tissues and cells by hyperthermia, and 2) utilize this knowledge in the treatment of cancer. To this end animal studies, in vitro cellular studies, and clinical studies are currently under way. The objective of the present proposal is to compare the responses of neoplastic and normal tissues of the mouse to local tumor hyperthermia (LTH) and radiation to evaluate the time-dose relationship of combined radiation and hyperthermia on the therapeutic ratio. It is proposed that these studies be carried out using a fibrosarcoma grown in BALB/c mice. Comparisons of the time-dose response of the tumor vs. normal tissues will help establish treatment parameters which will optimize the therapeutic ratio.